This invention relates to fuel-cell power plants, and more particularly to a fuel-cell power plant which employs an internal reforming type fuel cell.
FIG. 1 shows a prior-art power plant which employs an internal-reforming molten-carbonate type fuel cell. Referring to the figure, numeral 1 designates an internal-reforming molten-carbonate type fuel cell (hereinbelow, simply termed "fuel cell") which is made up of one or more laminated cell structures. A combustor 2 serves to oxidize a fuel gas unreacted in the fuel cell 1. Hezt exchangers 3a and 3b serve to preheat a reaction gas which is supplied to the fuel cell 1.
Owing to the above construction, the fuel gas 7 which consists of fuel 5, containing hydrocarbon or alcohols as its principal ingredient, and steam 6 is preheated to a predetermined temperature, for example, 550.degree. C. by the heat exchanger 3a and is thereafter supplied to the fuel cell 1. On the other hand, air 8 is mixed with an exhaust gas at the outlet of the combustor 2, the major ingredient of which is carbon dioxide perfectly oxidized by the combustor 2. The air 8 mixed with the exhaust gas is preheated by the heat exchanger 3b, and is thereafter supplied to the fuel cell 1.
Here, the fuel cell 1 uses as its fuel the fuel gas principally containing hydrocarbon or alcohols and operates at a temperature of or near 650.degree. C. by way of example. In a gas passage and an electrode on the fuel gas side of the fuel cell 1, there are carried out chemical reactions (Formulas (1)-(4) given below) of decomposing the hydrocarbon or alcohols to produce hydrogen and an electrochemical reaction (Formula (5) given below) of consuming the hydrogen to create electricity. Besides, in an electrode on the oxidizing gas side, an electrochemical reaction (Formula (6) given below) is conducted. The fuel cell 1 converts chemical energy inherent in the fuel gas into electric energy and its attendant thermal energy as a whole.